The Experts below are selected from a list of 319803 Experts worldwide ranked by ideXlab platform
Momoji Kubo - One of the best experts on this subject based on the ideXlab platform.
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development of a transferable reaxff Parameter Set for carbon and silicon based solid systems
Journal of Physical Chemistry C, 2020Co-Authors: Yang Wang, Yuqing Shi, Qiang Sun, Momoji KuboAbstract:The performance of carbon- and silicon-based solid lubricants is strongly affected by the tribochemical reactions, especially with hydrogen and oxygen. Even though understanding and unveiling these...
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development of a transferable reaxff Parameter Set for carbon and silicon based solid systems
The Journal of Physical Chemistry, 2020Co-Authors: Yang Wang, Yuqing Shi, Qiang Sun, Momoji KuboAbstract:The performance of carbon- and silicon-based solid lubricants is strongly affected by the tribochemical reactions, especially with hydrogen and oxygen. Even though understanding and unveiling these reaction dynamics are important to improve performance, these insights are difficult to be obtained by experiments. Molecular dynamics simulation using the reactive force field (ReaxFF) provides a way to study the detailed reaction dynamics at the atomic scale; however, there is no available ReaxFF Parameter Set which is able to handle all of the desired properties and tribochemical reactions regarding carbon- and silicon-based materials. Here, we succeed to develop a ReaxFF Parameter Set for the H/C/N/O/Si system which covers most of the current research targets on the carbon/silicon-based solid lubricants using the simulated annealing algorithm to fit with the first-principles calculations. This developed Parameter Set is able to well describe the chemical reactions of carbon- and silicon-based solids with conventional environmental reactants such as water, H₂, and O₂ molecules. Furthermore, to validate the developed Parameters, oxidation processes of SiC and Si₃N₄ in oxygen atmosphere are simulated and compared to the experimental results, showing good agreement. This well-trained ReaxFF Parameter Set is expected to benefit future studies on the tribochemical reactions and friction/wear mechanisms of carbon- and silicon-based lubricating systems.
Xifeng Fang - One of the best experts on this subject based on the ideXlab platform.
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improving mid tone quality of variable coefficient error diffusion using threshold modulation
International Conference on Computer Graphics and Interactive Techniques, 2003Co-Authors: Bingfeng Zhou, Xifeng FangAbstract:In this paper, we describe the use of threshold modulation to remove the visual artifacts contained in the variable-coefficient error-diffusion algorithm. To obtain a suitable Parameter Set for the threshold modulation, a cost function used for the search of optimal Parameters is designed. An optimal diffusion Parameter Set, as well as the corresponding threshold modulation strength values, is thus obtained. Experiments over this new Set of Parameters show that, compared with the original variable-coefficient error-diffusion algorithm, threshold modulation can remove visual anomalies more effectively. The result of the new algorithm is an artifact-free halftoning in the full range of intensities. Fourier analysis of the experimental results further support this conclusion.
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improving mid tone quality of variable coefficient error diffusion using threshold modulation
International Conference on Computer Graphics and Interactive Techniques, 2003Co-Authors: Bingfeng Zhou, Xifeng FangAbstract:In this paper, we describe the use of threshold modulation to remove the visual artifacts contained in the variable-coefficient error-diffusion algorithm. To obtain a suitable Parameter Set for the threshold modulation, a cost function used for the search of optimal Parameters is designed. An optimal diffusion Parameter Set, as well as the corresponding threshold modulation strength values, is thus obtained. Experiments over this new Set of Parameters show that, compared with the original variable-coefficient error-diffusion algorithm, threshold modulation can remove visual anomalies more effectively. The result of the new algorithm is an artifact-free halftoning in the full range of intensities. Fourier analysis of the experimental results further support this conclusion.
Yang Wang - One of the best experts on this subject based on the ideXlab platform.
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development of a transferable reaxff Parameter Set for carbon and silicon based solid systems
Journal of Physical Chemistry C, 2020Co-Authors: Yang Wang, Yuqing Shi, Qiang Sun, Momoji KuboAbstract:The performance of carbon- and silicon-based solid lubricants is strongly affected by the tribochemical reactions, especially with hydrogen and oxygen. Even though understanding and unveiling these...
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development of a transferable reaxff Parameter Set for carbon and silicon based solid systems
The Journal of Physical Chemistry, 2020Co-Authors: Yang Wang, Yuqing Shi, Qiang Sun, Momoji KuboAbstract:The performance of carbon- and silicon-based solid lubricants is strongly affected by the tribochemical reactions, especially with hydrogen and oxygen. Even though understanding and unveiling these reaction dynamics are important to improve performance, these insights are difficult to be obtained by experiments. Molecular dynamics simulation using the reactive force field (ReaxFF) provides a way to study the detailed reaction dynamics at the atomic scale; however, there is no available ReaxFF Parameter Set which is able to handle all of the desired properties and tribochemical reactions regarding carbon- and silicon-based materials. Here, we succeed to develop a ReaxFF Parameter Set for the H/C/N/O/Si system which covers most of the current research targets on the carbon/silicon-based solid lubricants using the simulated annealing algorithm to fit with the first-principles calculations. This developed Parameter Set is able to well describe the chemical reactions of carbon- and silicon-based solids with conventional environmental reactants such as water, H₂, and O₂ molecules. Furthermore, to validate the developed Parameters, oxidation processes of SiC and Si₃N₄ in oxygen atmosphere are simulated and compared to the experimental results, showing good agreement. This well-trained ReaxFF Parameter Set is expected to benefit future studies on the tribochemical reactions and friction/wear mechanisms of carbon- and silicon-based lubricating systems.
Bingfeng Zhou - One of the best experts on this subject based on the ideXlab platform.
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improving mid tone quality of variable coefficient error diffusion using threshold modulation
International Conference on Computer Graphics and Interactive Techniques, 2003Co-Authors: Bingfeng Zhou, Xifeng FangAbstract:In this paper, we describe the use of threshold modulation to remove the visual artifacts contained in the variable-coefficient error-diffusion algorithm. To obtain a suitable Parameter Set for the threshold modulation, a cost function used for the search of optimal Parameters is designed. An optimal diffusion Parameter Set, as well as the corresponding threshold modulation strength values, is thus obtained. Experiments over this new Set of Parameters show that, compared with the original variable-coefficient error-diffusion algorithm, threshold modulation can remove visual anomalies more effectively. The result of the new algorithm is an artifact-free halftoning in the full range of intensities. Fourier analysis of the experimental results further support this conclusion.
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improving mid tone quality of variable coefficient error diffusion using threshold modulation
International Conference on Computer Graphics and Interactive Techniques, 2003Co-Authors: Bingfeng Zhou, Xifeng FangAbstract:In this paper, we describe the use of threshold modulation to remove the visual artifacts contained in the variable-coefficient error-diffusion algorithm. To obtain a suitable Parameter Set for the threshold modulation, a cost function used for the search of optimal Parameters is designed. An optimal diffusion Parameter Set, as well as the corresponding threshold modulation strength values, is thus obtained. Experiments over this new Set of Parameters show that, compared with the original variable-coefficient error-diffusion algorithm, threshold modulation can remove visual anomalies more effectively. The result of the new algorithm is an artifact-free halftoning in the full range of intensities. Fourier analysis of the experimental results further support this conclusion.
Philippe H Hunenberger - One of the best experts on this subject based on the ideXlab platform.
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a gromos compatible force field for small organic molecules in the condensed phase the 2016h66 Parameter Set
Journal of Chemical Theory and Computation, 2016Co-Authors: Bruno A C Horta, Patrick F J Fuchs, Pascal T Merz, Jozica Dolenc, Sereina Riniker, Philippe H HunenbergerAbstract:This article reports on the calibration and validation of a new GROMOS-compatible Parameter Set 2016H66 for small organic molecules in the condensed phase. The calibration is based on 62 organic molecules spanning the chemical functions alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, amide, thiol, sulfide, and disulfide, as well as aromatic compounds and nucleic-acid bases. For 57 organic compounds, the calibration targets are the experimental pure-liquid density ρliq and the vaporization enthalpy ΔHvap, as well as the hydration free energy ΔGwat and the solvation free energy ΔGche in cyclohexane, at atmospheric pressure and at (or close to) room temperature. The final root-mean-square deviations (RMSD) for these four quantities over the Set of compounds are 32.4 kg m(-3), 3.5 kJ mol(-1), 4.1 kJ mol(-1), and 2.1 kJ mol(-1), respectively, and the corresponding average deviations (AVED) are 1.0 kg m(-3), 0.2 kJ mol(-1), 2.6 kJ mol(-1), and 1.0 kJ mol(-1), respectively. For the five nucleic-acid bases, the parametrization is performed by transferring the final 2016H66 Parameters from analogous organic compounds followed by a slight readjustment of the charges to reproduce the experimental water-to-chloroform transfer free energies ΔGtrn. The final RMSD for this quantity over the five bases is 1.7 kJ mol(-1), and the corresponding AVED is 0.8 kJ mol(-1). As an initial validation of the 2016H66 Set, seven additional thermodynamic, transport, and dielectric properties are calculated for the 57 organic compounds in the liquid phase. The agreement with experiment in terms of these additional properties is found to be reasonable, with significant deviations typically affecting either a specific chemical function or a specific molecule. This suggests that in most cases, a classical force-field description along with a careful parametrization against ρliq, ΔHvap, ΔGwat, and ΔGche results in a model that appropriately describes the liquid in terms of a wide spectrum of its physical properties.
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a gromos Parameter Set for vicinal diether functions properties of polyethyleneoxide and polyethyleneglycol
Journal of Chemical Theory and Computation, 2012Co-Authors: Patrick F J Fuchs, Philippe H Hunenberger, Halvor S Hansen, Bruno A C HortaAbstract:An extension 53A6OXY+D to the GROMOS 53A6OXY force field is reported that includes an accurate description of the vicinal diether function. The calibration is based on the model compound 1,2-dimethoxyethane (DXE) and involves a fitting of the relevant torsional-energy Parameters against quantum-mechanical (QM) rotational energy profiles for the OCCO and CCOC dihedral angles in vacuum, followed by a validation against experimental conformer populations in the pure liquid and in aqueous mixtures. A systematic comparison between the 53A6, 56A6CARBO, 53A6OXY, and 53A6OXY+D Parameter Sets is also performed in terms of these properties, as well as in terms of the thermodynamic properties of dimethylether (DME), diethylether (DEE), 1-methoxypropane (MPH), and DXE. Finally, the new Parameter Set is further validated in the context of polyethers, namely polyethyleneoxide (PEO) and polyethylenegycol (PEG). The 53A6OXY+D Set reproduces well the QM rotational profiles of DXE in vacuum (by calibration), the conformati...
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new interaction Parameters for oxygen compounds in the gromos force field improved pure liquid and solvation properties for alcohols ethers aldehydes ketones carboxylic acids and esters
Journal of Chemical Theory and Computation, 2011Co-Authors: Bruno A C Horta, Patrick F J Fuchs, Wilfred F Van Gunsteren, Philippe H HunenbergerAbstract:A new Parameter Set (53A6OXY) is developed for the GROMOS force field, that combines reoptimized Parameters for the oxygen-containing chemical functions (alcohols, ethers, aldehydes, ketones, carboxylic acids, and esters) with the current biomolecular force field version (53A6) for all other functions. In the context of oxygen-containing functions, the 53A6OXY Parameter Set is obtained by optimization of simulated pure-liquid properties, namely the density ρliq and enthalpy of vaporization ΔHvap, as well as solvation properties, namely the free energies of solvation in water ΔGwat and in cyclohexane ΔGche, against experimental data for 10 selected organic compounds, and further tested for 25 other compounds. The simultaneous refinement of atomic charges and Lennard-Jones interaction Parameters against the four mentioned types of properties provides a single Parameter Set for the simulation of both liquid and biomolecular systems. Small changes in the covalent Parameters controlling the geometry of the oxygen-containing chemical functions are also undertaken. The new 53A6OXY force-field Parameters reproduce the mentioned experimental data within root-mean-square deviations of 22.4 kg m(-3) (ρliq), 3.1 kJ mol(-1) (ΔHvap), 3.0 kJ mol(-1) (ΔGwat), and 1.7 kJ mol(-1) (ΔGche) for the 35 compounds considered.
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an improved nucleic acid Parameter Set for the gromos force field
Journal of Computational Chemistry, 2005Co-Authors: Thereza A Soares, Philippe H Hunenberger, Mika A Kastenholz, Roberto D Lins, Chris Oostenbrink, Vincent Krautler, Thomas Lenz, Wilfred F Van GunsterenAbstract:Over the past decades, the GROMOS force field for biomolecular simulation has primarily been developed for performing molecular dynamics (MD) simulations of polypeptides and, to a lesser extent, sugars. When applied to DNA, the 43A1 and 45A3 Parameter Sets of the years 1996 and 2001 produced rather flexible double-helical structures, in which the Watson-Crick hydrogen-bonding content was more limited than expected. To improve on the currently available Parameter Sets, the nucleotide backbone torsional-angle Parameters and the charge distribution of the nucleotide bases are reconsidered based on quantum-chemical data. The new 45A4 Parameter Set resulting from this refinement appears to perform well in terms of reproducing solution NMR data and canonical hydrogen bonding. The deviation between simulated and experimental observables is now of the same order of magnitude as the uncertainty in the experimental values themselves.
